Neuro opthalmology/vision path

Question 1

What innervates the globe and adnexa?

Answer 1

CN 2-8 and 10
ANS

Question 2

What is cranial nerve 2?

Answer 2

optic nerve
made of retinal ganglion
axons exit at optic disk
cross over at optic chiasm
optic tracts then to brain

Question 3

What does a lesion of CN 2 cause?

Answer 3

blindness
dilated pupils
absent PLR

Question 4

What is CN 3?

Answer 4

oculomotor nerve
inervates levator palpebrae superioris muscle (lifts eyelid)
provides motor fibers to all muscles except a few

Question 5

What muscles aren’t innervated by CN3?

Answer 5

LR6SO3
Lateral rectus (6)
Retractor bulbi (6)
superior/dorsal oblique (4)

Question 6

What do lesions of CN 3 cause?

Answer 6

dilated pupil
ventral lateral strabismus (down and out)
Ophthalmoplegia
ptosis

Question 7

What is cranial nerve 4?

Answer 7

trochlear nerve
innervates superior oblique
rare to have as isolated lesion
normally rotates dorsal globe medially
leasion causes extorsion (dorsal globe goes laterally)

Question 8

What is CN 5?

Answer 8

trigeminal nerve
3 branches

Question 9

What is the first branch of the trigeminal nerve?

Answer 9

ophthalmic
sensory fibers from cornea, conjunctiva, superior lid
afferent arm of oculocardiac reflex
lesions cause loss of sensation and decreased reflex tear production

Question 10

What is the second branch of CN 5?

Answer 10

maxillary branch
sensory to skin of lower lid
lesion causes loss of sensation

Question 11

What is the third branch of CN 5?

Answer 11

mandibular
motor to muscles of mastication
lesion causes muscle atrophy (globe sinks back)

Question 12

What is cranial nerve 6?

Answer 12

motor to lateral rectus and retractor bulbi
isolate lesion is rare
lesions cause
-medial globe deviation from LR
- inability to retract globe with RB

Question 13

What is CN 7?

Answer 13

motor to muscles of facial expression
-close eyelids (obicularis oculi)
-ear position, lip move, nares move

carries parasymp fibers to lacrimal gland

Question 14

What happens with a lesion at CN7

Answer 14

drooping superior lid (ptosis)
incomplete blink
decreased lacrimation
abnormalities of ear, lip, nares, position and movement

can be caused by otitis, hypothyroidism, trauma, etc

Question 15

What is CN 8?

Answer 15

vestibular nerve

Afferent component of ocular position
controls EOM position so remain fixed on object while head turns
eyes can track smoothly
lesions cause eye drop/ nystagmus

Question 16

What does cranial nerve 10 do?

Answer 16

Vagus
efferent arm of oculocardiac reflex
intaoperative handling of the eye causes brachycardia

Question 17

What is the sympathetic pathway?

Answer 17

1st neuron=midbrain to T1-T3
2nd neuron= thorax
3rd= cranial cervical ganglion to eye

Question 18

What do sympathetic nerves innervate?

Answer 18

pupillary dilator muscle
smooth muscle in orbit and upper, lower, third eyelid

Question 19

What are the signs of horner’s syndrome?

Answer 19

ptosis (droopy lid)
enophthalmus ( sunken globe)
protrusion of nictitians
miosis (small pupil)
vasodilation of affected side
unilateral sweating

Question 20

What are ANS parasymp pupillary fibers and what do they do?

Answer 20

originate in PS nucleus of CN 3 (EWN)
travel with CN 3 to ciliary ganglion
enter globe as short ciliary nerves
act to constrict pupil
lesion causes dilated pupils

Question 21

What are ANS parasymp lacrimal gland fibers? What do they do?

Answer 21

efferent arm of lacrimation
fibers travel with CN 7
lesion= decreased tear production

Dry eye, dry nose, dilated pupil

Question 22

What are the parts of the vision pathway?

Answer 22

optical
photochemical
neurologic transmission/processing

Question 23

What is the optical path?

Answer 23

light
cornea
lens
retina
image is reversed and upside down on retina

Question 24

What is phototransduction?

Answer 24

cells convert photons of light to energy
occurs in photoreceptors

Question 25

What is signal transduction?

Answer 25

photoreceptors communicate with bipolar cells amacrine cells retinal ganglion cells axons optic nerve=sends signal to visual cortex for processing

Question 26

What is the track of the optic nerve?

Answer 26

axons convers and exit at optic disk axons form optic nerve medial axons of ON cross at optic chiasm travel as optic tract to LGN

Question 27

What does crossing over of ON do?

Answer 27

integrates images from each eye

Question 28

How is the image reflexted on retina and ON/

Answer 28

If image is medial- optic nerve and retinal is lateral vice versa Lateral pathways cross over, medial do not lateral is monocular, medial is binocular

Question 29

What is the meance response?

Answer 29

Afferent: retina and ON Efferent CN7 and muscles of head cover one eye, test medial and lateral visual fields normal is blink

Question 30

What is the cottonball test?

Answer 30

throw cotton ball in air and then watch to see if head and eyes follow it

Question 31

Describe the steps in the vision pathway

Answer 31

retina/optic nerve chiasm optic tracts lateral geniculate nucleus optic radiations visual cortex

Question 32

What is the afferent and efferent response of the pupillary light reflex?

Answer 32

A- retian and ON to chiasm to optic tract to pretectal nucleus and central decussation to EWN E- parasymp fibers of EWN travel with CN 3 to spinchter

Question 33

Where does the PRL differ from the vision pathway?

Answer 33

At the level of the LGN

Question 34

What occurs if a lesion in the afferent arm of the PLR before LGN?

Answer 34

absent PLR and blindness

Question 35

What happens if there is a lesion from LGN to visual cortex

Answer 35

blind still have normal PLR

Question 36

Waht happens if there is a lesion in the efferent PLR pathway?

Answer 36

not blind abnormal PLR response

Question 37

What happens with a unilateral lesion of the optic nerve as an afferent deficit?

Answer 37

Side with lesion will not constrict and opposite side will not (no crossing over). Side without lesion will cause both eyes to constrict. eye with lesion is blind

Question 38

What can cause afferent PLR deficits?

Answer 38

glaucoma retinal detachment

Question 39

What happens to PLR with a unilateral efferent deficit

Answer 39

eye with lesion won't constrict but opposite will. if stim opposite eye, direct stimulation but affected eye doesn't constrict

Question 40

What can cause efferent PLR deficits ?

Answer 40

Iris atrophy posterior synechia atropine